Achieving remarkable success in his studies[1] at the seminary of Saint-Sulpice and the Sorbonne, the death of his elder brother made him the head of his family, and giving up his birthright, he dedicated his life to the Catholic Church.

[1] He rose rapidly through the hierarchy of the church, first made Vicar-General of Pontoise; then in 1765 he was created Bishop of Lavaur;[1] and on 4 November 1770 he was appointed Archbishop of Aix in Provence.

When in a time of scarcity and of political ferment, at the outset of the French Revolution, Aix was threatened with violence and famine, the archbishop by his firmness, great ascendancy, wisdom, and generosity, proved its savior.

The mob had pillaged the public granaries, and had answered by insults the summons of authority; as president of the Estates of Provence, Boisgelin assembled the magistrates, chief citizens, and merchants, dispelled their fears, and prevailed upon these men to procure for Aix an abundant supply of grain, towards the payment of which he contributed one hundred thousand livres.

It denied the supreme jurisdiction of the pope, subjected ecclesiastics to the civil power, and decreed that all the members of the clergy, beginning with those in the assembly, should take the oath of allegiance to the constitution, under penalty of exile and the forfeiture of their salaries.

In his answer to a letter from Edmund Burke in which the orator expressed his admiration for the spirit of disinterestedness and dignity of character of the French episcopacy, he complained that he was expelled from France in the name of that liberty he had in perfect faith contributed to establish, and under whose protection he hoped to end his days.